The present disclosure relates to an apparatus and a method for beamforming in a wireless communication system having a two dimensional plane antenna array.
As a core communication technology in a next generation wireless communication system, a massive Multiple-Input Multiple-Output (MIMO) technology is being researched. In the massive MIMO technology, a base station using a large number (e.g., hundreds) of transmission antennas supports a multi-user based on a MIMO technology.
In theory, a transmit beam forming gain is in proportion to the number of transmission antennas. Accordingly, a massive MIMO system uses a high beamforming gain, so that each transmission antenna may use low transmission power. Therefore, the massive MIMO technology is being magnified as a main technology of green communication.
Particularly, as a cell becomes smaller in a wireless communication system, research on the massive MIMO system (hereinafter, referred to as a “planar massive MIMO system”) using a two dimensional planar array antenna is actively being progressed. According to the planar massive MIMO system, an increase in capacity by two dimensional beamforming and Space Division Multiple Access (SDMA) in a horizontal dimension and a vertical dimension is possible.
The planar massive MIMO system supports two dimensional beamforming. The two dimensional beamforming by the planar massive MIMO system minutely divides service areas corresponding to all cells two-dimensionally, and may selectively transmit or may not transmit a signal to each of the divided areas.
Further, as another core communication technology in the next generation wireless communication system, many researches on Heterogeneous Networks (HetNet) which can increase spectral efficiency are being progressed. The heterogeneous networks has, for example, a structure in which a service area by at least one small eNB (hereinafter, referred to as a “small service area”) overlaps a service area by a macro eNB (hereinafter, referred to as a “macro service area”). That is, in the structure, a small cell corresponding to at least one small service area overlaps a large cell corresponding to the macro service area.
However, the increase in the spectral efficiency in the heterogeneous network is limited by Inter-Cell Interference (ICI) between the macro eNB and the small eNB. Accordingly, for the increase in the spectral efficiency in the heterogeneous network, it is required to develop a technology to effectively avoid the ICI.